Method of preparation of rare earth (iii) phosphorus dichloridates and phosphorus dibromidates

ABSTRACT

A novel and desirable method of preparing a rare earth (III) phosphorus dichloridate comprises the steps of adding a rare earth trifluoroacetate to phosphorus oxychloride, refluxing the mixture and then washing the resultant percipitate under a dry atmosphere to remove excess moisture and phosphorus oxychloride. The method may also be employed in preparation of a rare earth (III) phosphorus dibromidate by the analagous steps of adding a rare earth trifluoroacetate to phosphorus oxybromide, refluxing the mixture, and finally washing the resultant precipitate under dry atmosphere to remove the excess moisture and phosphorus oxybromide. Any of the rare earths may be employed in their trifluoroacetate form except those which are radio active, and, though not limited to the preparation of neodymium (III) phosphorus dichloridate, the method is particularly desirable in that instance because of the fact that neodymium (III) phosphorus dichloridate is highly desirable in liquid laser compositions.

United States Patent Schimitschek et al.

[451 Oct. 17, 1972 [54] METHOD OF PREPARATION OF RARE EARTH (III) PHOSPHORUS DICHLORIDATES AND PHOSPHORUS DIBROMIDATES 72] Inventors: Erhard J. Schimitschek, Garching/Munich, Germany; John A. Trias, La Mesa, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy 22 Filed: Jan. 29, 1971 21 Appl.No.: 110,920

[52] U.S. Cl. ..423/263, 423/300, 260/544,

260/664 [51] Int. Cl. ..C22b 59/00 [58] Field of Search ..23/20, 22, 105, 368

[56] References Cited OTHER PUBLICATIONS Kauffmann et al., Zeitschrift fur Anorganische und Allgemeine Chemie Vol. 347, 1966, pp. 318- 326. Muller et al., Zeitschrift fur Anorganische und Allgemeine Chemie, Vol. 350, 1967, pp. 231- 236.

Primary Examiner-Herbert T. Carter I Att0rney-R. S. Sciascia, G. J. Rubens and J. W. McLaren [57] ABSTRACT refluxing the mixture, and finally washing the resultant precipitate under dry atmosphere to remove the excess moisture and phosphorus oxybromide. Any of the rare earths may be employed in their trifluoroacetate form except those which are radio active, and, though not limited to the preparation of neodymium (III) phosphorus dichloridate, the method is particularly desirable in that instance because of the fact that neodymium (III) phosphorus dichloridate is highly desirable in liquid laser compositions.

9 Claims, 1 Drawing Figure PATENTEDHBI 11 m2 I 3.69921 1 g ,T z I o O O O -\PX2 g 3 o o Nd--O x g INVENTORS ERHARD J. SCHIMITSCHEK y A%TRIAS ATTORNEYS preparation of a METHOD OF PREPARATION OF RARE EARTH (III) PHOSPHORUS DICHLORIDATES AND PHOSPHORUS DIBROMIDATES STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE'INVENTION Although many of the organic derivatives of phosphorus-dichloridic and phosphorous-dibromidic acid are known, relatively few inorganic salts have been prepared. In recent scientific publications the prior art has described the preparation and properties of thorium, aluminum, gallium, indium, iron and beryllium phosphorous dichloridates. The prior art method of preparation of such compositions has consisted of dissolving the respective anhydrous metal chloride in phosphorus oxychloride and then introducing chlorine mono-oxide; that reaction might be represented as: MCI, 3POCI 301 M(O PCI 6Cl (I) This method as employed with neodymium trichloride, required dissolution in phosphorus oxychloride which would, upon the introduction of chlorine mono-oxide, produce a neodymium (III) phosphorus dichloridate and also chlorine gas. While this method of preparation produced the desired compound, it was also undesirable and cumbersome in the aspects of handling and dealing with the gases chlorine mono-oxide and chlorine, particularly in view of their highly corrosive and noxious nature.

The production of neodymium (III) phosphorus dichloridate is of particular interest because of its use in a liquid laser composition as disclosed by E. J. Schimitschek and J. A. Trias of the Naval Electronics Laboratory Center, San Diego, California, in a paper presented at the Sixth International Quantum Eleqtronics Conference in September 1970 held in Kyoto, Japan. Accordingly, an improved method and technique for the production of that particular rare earth phosphorus dichloridate is highly desirable.

SUMMARY OF THE INVENTION The concept of the present invention comprises a method of preparing a rare earth (III) phosphorus dichloridate or a rare earth (III) phosphorus dibromidate. In the method for preparing a rare earth (Ill) phosphorus dichloridate the steps include adding a rare earth trifluoroacetate to phosphorus oxychloride,

refluxing the mixture thoroughly, and washing the resultant percipitate under dry atmosphere, for example, to thoroughly remove excess moisture and phosphorus oxychloride. This is required because of the highly hygroscopic nature of the resultant rare earth (Ill) phosphorus dichloridate precipitate.

The concept of the present invention also includes rare earth (III) phosphorus dibromidate by performing the steps of adding a rare earth trifluoroacetate to phosphorus oxybromide, refluxing the mixture, and then washing the resultant percipitate under a dry atmosphere to thoroughly remove excess moisture, as well as excess phosphorus oxybromide.

It will be obvious to those skilled in the art that a compound highly desirable for use in a liquid lasing composition, namely neodymium (Ill) phosphorus dichloridate, may be produced by the novel method conceived by the present invention without the use of chlorine mono-oxide and without producing chlorine gas by the reaction. Moreover, the present invention conceives the production of numerous rare earth (Ill) phosphorus dichloridates and rare earth (III) phosphorus dibromidates including those wherein the rare earth may be lanthanum, cerium, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, as well as neodymium.

Accordingly, it is a primary object of the present invention to provide an improved method of preparing rare earth (III) phosphorus dichloridates and rare earth (III) phosphorus dibromidates.

Another most important object of the present invention is to provide such a method which eliminates the need for a gas such as chlorine mono-oxide to promote the reaction producing the desired resultant compound.

Still another most important object of the present invention is to provide an improved method of preparation as described above wherein the concommitant reaction does not produce a gas such as the noxious and corrosive chlorine produced in prior art methods of preparation of comparable compounds.

A further object of the present invention is to devise a method of preparing rare earth (III) phosphorus compounds in both dichloridic and dibromidic forms.

These and other objects, featuresand advantages of the present invention will be better appreciated from an understanding of the disclosure of the novel method of preparation described hereinafter.

DESCRIPTION OF THE DRAWING The drawing illustrates a proposed structure for d Q PX 9 Wh re as/- .eit eri hlqri e bromine.

DESCRIPTION OF THE PREFERRED METHOD In the prior art method of the preparation of metallic phosphorus dichloridates, such as exemplified by the chemical reaction represented in the foregoing Equation (1), the respective anhydrous metal chloride was dissolved in phosphorus oxychloride and thereafter chlorine monooxide was introduced into the solution. If it is desired, however, to prepare neodymium (III) phosphorus dichloridate it will be found that anhydrous neodymium trichloride is not soluble in phosphorus oxychloride; however,neodymium trifluoroacetate does dissolve in phosphorus oxychloride and therefore a reaction may be brought about immediately without the introduction of chlorine mono-oxide. This reaction may be represented as follows:

90.9)3 la Cl2)3 During the reaction represented above, trifluoroacetyl chloride, which has a boiling point of 18 C., escapes and may be positively identified by comparing its vapor phase infrared spectrum with a commercial sample of trifluoroacetyl chloride, for example. The solid product which is not soluble in the phosphorus oxychloride maybe easily separated from the excess-phosphorus oxychloride and then dried.

The same method as described hereinbefore may be applied to the preparation of neodymium (Ill) phosphorus dibromidate by substituting phosphorus oxybromide for the phosphorus oxychloride in the procedure.v Both materials are very hygroscopic and react with water and alcohols. However, they do not dissolve in the none-or low-polar solvents, but do dissolve in highly polar solvents like dimethyl sulfoxide or dimethyl formamide. The neodymium (lll) phosphorus dichloridate is a light blue powder, whereasneodymium (Ill) dibromidate is a reddish-grey powder. No melting point was. observed foreither compound up to The infrared absorption spectra of these two compounds indicate at least partial covalency of the Nd-O bond and furthermore, an approximate D symmetry at the Nd site. This, in addition to the chemical behavior, i.e., high thermal stability, and low solubility may be interpreted to be evidence of polymerization. X-ray measurements on related-compounds, such as M,,(PO Cl )2'( 3b 2 )3 and 2 2)2'( a 2 revealed that the O PX -groups (X ='F,Cl, Br,) easily bridge neighboring metal ions, forming eight membered rings. It is therefore suggested that Nd(O PCl and Nd(O,PBr may comprise a similar proposed structure such as illustrated in FIG. 1 which would also account for an approximate D symmetry.

Although as mentioned hereinbefore, Nd(O PCl does not dissolve in POCl it does go into solution after adding a tetra-valent metal chloride, like ZrCh, in a ratio of 1:1 or higher. The ZrCl 1apparently opens the O PCI -bridges by coordination to the oxygens so that at least partial solvation of the neodymium with the POCI}, can occur. One of the primary interests in these solutions, typically 0.2M Nd(O PCl and 0.4M ZrCl is stimulated by their application in liquid lasers such as the improved liquid lasing composition disclosed in copending patent application Ser. No. 111,128, titled A Liquid Laser Solution Formed with a Neodymium Salt in Phosphorus Oxychloride, and filed Jan. 29, 1971 in the names of applicants herein.

PREPARATION PROCEDURE For the preparation of Nd(O PCl 0.5 gr of anhydrous Nd(CF COO) and 3 ml of POCl (distilled) were added to 20 ml of CC 1 an inert, non-reactive solvent employed to facilitate the reaction. The mixture was gently refluxed for 1 hour, and the resulting precipitate was-carefully washed under dry atmosphere to remove excessmoisture and POCl The CCl, and some solvated POCl were removed by dryingunder vacuum at 100 C. for approximately hours. The product, obtained in essentially 100 percent yield, was a free flowing powder. The same procedure was followed to prepare Nd(O PBr but the 3 ml POCl was replaced by 5 gr of POBr The Nd(CF COO) was prepared by dissolving Nd O .in diluted CF COOH, driving most of the water out through heating,.and finally drying the product at 60 C. under vacuum for 5 days.

As may be readily appreciated by those skilled and knowledgeable in the art, the method of the present invention provides a direct reactionary process for the preparation of rare earth (Ill) phosphorus dichloridates and rare earth (III) phosphorus dibromidates which eliminates the need to introduce chlorine mono-oxide into a mixture as was done in prior artpractices, and, as is equally important, .also eliminates the production of chlorine gas as a result of the reaction.

As will be equally well appreciated by those knowledgeable and skilled in the art, the preparation of rare earth (III) phosphorus dichloridates and rare earth (Ill) phosphorus dibromidates by the improved method of the-present invention is of particular current interest because of the highly desirable results obtained with several of these compounds when they are employed in liquid lasing compositions, though the concept and teachings of the present invention in no way limit the usages of the resultant compounds.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A method of preparing a rare earth (Ill) phosphorus dichloridate comprising the steps of:

reacting a rare earth trifluoroacetate phosphorus oxychloride;

refluxing the'mixture; and,

washing the resultant precipitate under .dry atmosphere to remove the excess phosphorus oxychloride.

2. A method of preparing a rare earth (lll) phosphorus dichloridate as claimed in claim -1 wherein neodymium trifluoroacetate is reacted with phosphorus oxychloridate.

3. A method of preparing a rare earth (III) phosphorus dichloridate as claimed in claim 1 wherein the rare earth trifluoroacetate reacted with phosphorus oxychloride is that of one of the rare earths: lanthanum, cerium, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

4. A method of preparing a rare earth (III) phosphorus dibromidate comprising the steps of:

reacting a rare earth trifluoroacetate phosphorus oxybromide;

refluxing the mixture; and,

washing the resultant precipitate under dry atmosphere to remove the excess phosphorus oxybromide. 5. A method of preparing a rare earth (Ill) phosphorus dibromidate as claimed in claim 4 wherein the rare earth trifluoroacetate reacted with phosphorus with with

oxybromide is that of one of the rare earths:

lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbeium, and luteti- 6. A method of preparing a rare earth 111 phosphorus dichloridate as claimed in claim 1 wherein the rare earth trifluoroacetate reacts with phosphorus oxychloride in an inert, non-reactive solvent.

7. A method of preparing a rare earth lll phosphorus dichloridate as claimed in claim 6 wherein said solvent is carbon tetrachloride.

8. A method of preparing a rare earth Ill phosphorus dibromidate as claimed in claim 4 wherein the rare earth trifluoroacetate reacts with phosphorus oxybromide in an inert non-reactive solvent. I

9. A method of preparing a rare earth 111 phosphorus 5 dibromidate as claimed in claim 8 wherein said solvent is carbon tetrachloride. 

2. A method of preparing a rare earth (III) phosphorus dichloridate as claimed in claim 1 wherein neodymium trifluoroacetate is reacted with phosphorus oxychloridate.
 3. A method of preparing a rare earth (III) phosphorus dichloridate as claimed in claim 1 wherein the rare earth trifluoroacetate reacted with phosphorus oxychloride is that of one of the rare earths: lanthanum, cerium, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.
 4. A method of preparing a rare earth (III) phosphorus dibromidate comprising the steps of: reacting a rare earth trifluoroacetate with phosphorus oxybromide; refluxing the mixture; and, washing the resultant precipitate under dry atmosphere to remove the excess phosphorus oxybromide.
 5. A method of preparing a rare earth (III) phosphorus dibromidate as claimed in claim 4 wherein the rare earth trifluoroacetate reacted with phosphorus oxybromide is that of one of the rare earths: lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbeium, and lutetium.
 6. A method of preparing a rare earth III phosphorus dichloridate as claimed in claim 1 wherein the rare earth trifluoroacetate reacts with phosphorus oxychloride in an inert, non-reactive solvent.
 7. A method of preparing a rare earth III phosphorus dichloridate as claimed in claim 6 wherein said solvent is carbon tetrachloride.
 8. A method of preparing a rare earth III phosphorus dibromidate as claimed in claim 4 wherein the rare earth trifluoroacetate reacts with phosphorus oxybromide in an inert non-reactive solvent.
 9. A method of preparing a rare earth III phosphorus dibromidate as claimed in claim 8 wherein said solvent is carbon tetrachloride. 